Gaseous electric discharge lamp device



Dec. 21, 1937.

M. J. DRUYVESTEYN GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Filed Aug. 16,1937 INVENTOR Mari J. oru ves'teyn BY I ATTORNEY Patented Dec. 21, I937GASEOUS ELECTRIC DISCHARGE DEVICE f Mari J. Druyvesteyn,EindhovemNetherlands, asslgnor to General Electric Company; acorporationof New York Application August 16, 1937, Serial No.

In Germany August28, 1936,

2 Claimsr The present invention relates to gaseous-electric dischargelamp devices generally and more particularly the invention relates tosuch devices the gaseous atmosphere of which consists of or ,5.comprises a metalvapor. The container glasses, used for incandescentlamps and electric discharge lamps containing only a fixed gas are not"suitable for use in con-' nection with a discharge lamp containing achemically active metal For this reason these discharge devices are madeof special glasses, or the inside .of the glass wall as possible to themetal vapors. The composition of this glass or coating naturally dependson the I particular metal vapor used.

I have observed that occasionally the wall material is more resistant tothe metal vapor than to the solid or liquid metal from which the vaporis developed. This is particularly true in the case of a magnesium orthallium vapor discharge device. In such tubes the wall can be maderesistant to themetal vapor, but the useful life thereof is shortened bythe attack on the wall during operation by the surplus'metal in thetube,which is not vaporized, whereby theiwall soon loses its mechanicalproperties and the tube breaks after a short period of operation.

The object of the present invention is to prevent the unvaporizedportion of the metal from attacking the container of gaseous electricdischarge lamp devices of the above type. Still further objects andadvantages attaching to the device and to its use and parent to thoseskilled in the art from the following particular description.

The invention attains its object by providing a condensing surface onthe container which surface consists of a material resistant to theeflects of said metal in the solid, and which is interposed between theunvaporized metal and the wall of the container. This structure preventsthe attack of the unvaporized metal on the container glassand thegaseous electric discharge lamp device has a long, useful operatinglife. The condensing surface must be at a lower 50 temperature than theother. parts of the' container during the operation of the device andvarious means are useful for maintaining the pro tive layer at thenecessary temperature' For example, the heat losses from that part of-.55 the container wall covered by the protective layer in relation tothe heat losses from the remaining part of said wall are increased. Forexample, the part covered by the protective layer is made rough or blackon the outside to increase so the heat radiation locally. The containercan v layerextends in the is covered wlthsubstances which are asresistant operation will be ap-' liquid or vapor state (Cl. 176-122) Ialso be formed in sucha manner that the covered part of the wall isheatedless by the dis-' charge than the other parts. of the wall. Inthis casethe container ,is so constructed that the first mentioned-partof the wall is farther removed from the discharge paththan-the lastmentionedpa'rt,

Preferably, the container is of tubular shape and the protective layeris arranged between the electrodes so that'the vaporizable metal is.near the discharge path. Preferably, theprotective direction of the tubeaxis and has an oblong form. i I v The protective layershould be of suchthicknessthat the vaporizable metal cannot penetrate through it; Inamagnesium vapor discharge tube a layer of zirconium in g fixed to thecontainer wall is preferred. One can also use an aluminum oxide layer ofappreciable thickness. I In the drawing accompanying and forming part ofthis specification an embodiment Lofthe invention is shown, in which v sFig. 1 is a side elevational, partly sectional view of a gaseouselectric discharge lamp device embodying the invention and g 1 Fig; 2 isa sectional view along the line 2-2 of Fig.1. Referring to the drawingthe gaseous electric discharge lamp device comprises a tubular containerI having two thermior'iic. activated electrodes ,2 sealed therein, oneat each end thereof. Said electrodes are mounted closely adjacent therespective ends of the container l to maintain said ends at anelevatedtemperature during the operation of the device. Said electrodes 2 eachFICE-1.:

the form of a thinfoil afhave a pair of current leads and consist of acomposition:-

, Per cent S10: 78 A120: 12 Cab 10 a tungsten filament, of high electronemis- This glass is covered on the inside with a magnesium oxide skin.This skin is applied by the following method. The container -l is firsteva-cuated and heated to about 500 C.,'then magnesium vapor is passedthrough the container I until a slight attack of the glass is observed Iwithout the latter showing a noticeable chemical" in the glass surfaceis oxidized and the slight dischange. Thereupon moist air is admittedinto the container I and the latter is heatedto about 600 0., wherebythe magnesium which is on and coloration of the glass, which is causedby the physical attack of the glass, disappears. This magnesium oxideskin makes the container wall very resistant to magnesium vapor. Howeverat the elevated operating temperatureof the container it is lessresistant to the magnesium which is not vaporized. In order to avoidthis disadvantage, a thin strip 3 consisting of zirconium is applied onthe inside of the tube wall, which strip, for instance, is pasted on thecontainer j wall with the aid of water-glass and covers only arelatively small'partof the wall as shown in the drawing. That part ofthe outside of the container wall, which lies opposite this'zirconiu'mstrip, is provided with a black coating 4 consist= ing for instance ofcarbon. V

The tube contains a rare; starting gas consist ing of neon, for example,at a pressure of about 12 mm. Aside from this there is on the zirconiumlayer 3 in thetube, a quantity of magnesium which during operationfurnishes the necessary magnesium vapor.

The black layer 4 locally increases the heat loss,

so that the zirconium strip is the coldest part of the containerenclosing the discharge space. To avoid cold spaces behind theelectrodesI, these are arranged near the ends of the container I. Whendesired, the ends of the container are coated on the outside withplatinum mirrors to reduce the heat loss of said ends.

Sometimes temperatures can be permitted in the spaces behind theelectrodes which are somewhat lower than the lowest temperature of thezirconium strip, if care is taken to avoid distillation of the magnesiumover into these spaces behind the electrodes. For this purpose thesespaces can, for instance, be closed oil! with the aid of screens orseptums, or the tube wall can be so contracted that practically nomagnesium vapor gets into the spaces behind the electrodes.

that various omissions, substitutions and changes in the forms anddetails of the device illustrated and in its use and operation may bemade by those skilled in the art without departing from the broad spiritand scope of the invention, for

example, the lamp device is mounted in a heat conservator, such as adouble walled flask, when desired. 7

WhatI claim as new and desire to secure by Letters Patent of the UnitedStates, is:-

1. Afigaseous electric discharge device comprisingacontainer, electrodessealed therein, a quantity or vaporizable metal therein the vapor ofwhich is luminosity producing during the operationof the device, theinner wall of said container being resistant to the 'hot, ionized metalvapor and being subject to attack by the unvaporized'portion of saidmetal, a condensing surface on said container and a material inert withrespect to'said metal in any state interposed between said surface andthe unvaporized portion of said metal and covering said surface toprotect said surface from the deleterious effects of said unvaporizedmetal. V v 2. A gaseous electric discharge device comprising anelongated, tubular container, electrodes sealed therein at the endsthereof, ,a quantity of vaporizable metal therein the vapor of which isluminosity producing during the operation of the device, the inner wallof said container being resistant to the hot, ionized metal vapor andbeing subject to attack by the unvaporized portion of'said metal, acondensing surface on said container, said surface extendinglongitudinally along said container between said electrodes, and amaterial inert with respect to said metal in any, state interposedbetween said surface and the unvaporized portion of said metal andcovering said surface to protect said surface from the deleteriouseffects of said unvaporized metal.

' MARI J. DRUYVESTEYN.

